cputime: Clean up cputime_to_usecs and usecs_to_cputime macros

Get rid of semicolon so that those expressions can be used also
somewhere else than just in an assignment.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Dave Jones <davej@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Link: http://lkml.kernel.org/r/7565417ce30d7e6b1ddc169843af0777dbf66e75.1314172057.git.mhocko@suse.cz
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>